[llvm] [VPlan] Allow folding not (cmp eq) -> icmp ne with other select users (PR #154497)

[Ramkumar Ramachandra via llvm-commits]

artagnon wrote:

I can recommend rebasing this over https://github.com/llvm/llvm-project/pull/154771, once that lands.

https://github.com/llvm/llvm-project/pull/154497